The total mass of the system is 7.90 ± 0.21×1017 kg. For a realistic minimal density of 0.5 g/cm3 the albedo is >0.17 and the size of the components is <60 km.[3] The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.1 and calculates a diameter of 175.20 kilometers based on an absolute magnitude of 6.9.[5]

Mors–Somnus has an ultra-red spectrum in the visible and near-infrared parts of the spectrum. The colors of two components are indistinguishable from each other.[3] It demonstrates a double-peaked light curve with the period of about 9.28 hours and amplitude of 0.24. This indicates that either primary of secondary has an elongated shape and rotates non-synchronuosly.[6]